785.271.5816 | info@fsea.com



Technology Feature

Specialty UV Coatings: The “Finishing Touch” for Off-Line Finishing Projects

by Kris Getty, Henkel Corporation

November/December, 2009
Specialty UV coatings can serve an important role in any off-line finishing project. The latest specialty UV coating technologies appeal to virtually all the senses, delivering tremendous visual and other sensory appeal to any finishing project. What’s more, most of these coatings can be applied using standard finishing equipment in use today, such as Steinemann, Billhöfer, and Sakurai coaters. And because they are all UV coatings, these technologies offer all the benefits associated with UV (i.e., instant curing). Some of these coatings are an alternative to film laminations or laminated visual effects, providing further benefits in recyclability and ease of use.

Although many of these technologies have been around for several years, there are some new specialty coatings and coating techniques being used to deliver eye-popping effects. This article will explore some of the latest technologies that are commercially available.

Coating Effect

Screen

Flexo

Roller/
Blanket

Litho Ink
Station

Gloss/Matte Contrast

 

x

x

x*

Thermochromic

x

x

x

x

Raised (Embossed Effect)

x

x

 

 

Texture

x

x

x

 

Glitter

x

x

 

 

Pearlescent

x

x

x

x

Scratch-off

x

 

x

 

Glow-in-the-Dark

x

x

x

 

Metallic (Foil Effect)

x

x

x

x**

Holographic

 

x

x

 

Soft Touch

x

x

x

 

*Combine ink station + flexo coater to do in one step
**Will not achieve high brilliance with this method

Gloss/Matte Contrast
Most are familiar with gloss UV coatings that provide a high level of sheen or gloss, as well as matte coatings which give a dull effect. Both types can be applied in a spot application or overall pattern. These coatings can deliver high clarity, outstanding flexibility, and rub resistance that rivals or exceeds film lamination. However, the combination of these two technologies on the same printed piece can maximize the visual contrast between the gloss areas and matte areas. The result is that the glossy areas jump out at the viewer. This effect can actually be achieved in one pass on a litho press using a special type of coating called a “strike-through” varnish. This matte varnish is applied on the last litho unit of the press and is printed only on the areas where a matte effect is desired. The entire sheet then is immediately flood coated with a gloss coating and then UV-cured. Although the gloss coating is applied on top of the matte varnish, the matte coating actually over-powers the gloss and “strikes through” to the surface, creating a dull look. In areas where there is no matte varnish applied, the gloss coating is allowed to shine. Because the gloss coating is applied as a flood coating, this technique creates excellent contrast in a one-pass operation without the registration issues and the need for a special printing plate.

Thermochromic
Also known as thermochromatic coating, this type of coating actually changes colors with temperature. This effect often is used to conceal type or graphics so that prizes, offers, and messages can be revealed only when over-rubbed. The heat from the friction caused by rubbing causes the coating to change colors. Thermochromic coatings typically are available in various colors and temperature ranges (4o C and 37o C). Beer producers have used this technology to indicate when their product is chilled.

Raised or Embossed
This type of finish is created with a special high-viscosity UV coating that is applied in a heavy pattern to exhibit a unique dimensional profile that is comparable to mechanical embossing. Capable of being applied to a thickness in excess of 5 mils, these coatings provide excellent gloss, clarity, and protection of any piece. The result is a dramatic appearance that can bring to life snow on a mountainside, raindrops on a window, the leather of a jacket, or a myriad of other effects.

Texture
This type of finish creates a wrinkle-like or orange peel appearance. It can be applied with screen, roll coater, or flexo application. With these coatings, printers can spot-apply or coat entire areas to provide dimensional finishes that can range from the look of leather to frosted glass.

Glitter
Glitter is typically comprised of finely cut squares of metalized film. It can be used in combination with raised/embossed or specially engineered UV gloss coatings. The embossed/glitter combination allows designers to create unique specialized effects with different colors, shapes, and dimensions. In addition, emboss/glitter combinations can be applied to a thickness in excess of 5 mils and provide excellent gloss and clarity to any printed piece. Glitter coatings are supplied in various colors and cut sizes. Some coatings suppliers provide coatings with pre-mixed glitter. Other coatings suppliers provide the UV base coating and glitter needs to be mixed in at the correct level by the user.

Pearlescent
These coatings also are used in combination with emboss or specially engineered UV gloss coatings. By combining a very small discrete particle of a shimmering pearlized compound with a gloss coating, designers can create their own unique personalized effects using different colors, shapes, and dimensions. The effect is a rich, pearly finish. As with glitter, some coatings suppliers provide coatings with pre-mixed pearlescent compound. Other coatings suppliers provide the UV base coating and the pearlescent compound needs to be mixed in at the correct level by the user.

Scratch-off
Scratch-off coatings are available in UV, water-based, and solvent-based chemistries. UV scratch-off coatings must be used in combination with a special UV-curable primer in order to deliver the required level of release. Most scratch-off coatings deliver high opacity and scratch-off characteristics in advertising/specialty promotion coupon applications for department stores and supermarkets.

Glow-in-the-Dark
Glow-in-the-dark coatings exhibit phosphorescence, which results in a bright glowing effect, similar to what is used on specialty wrist watches. These coatings are relatively costly, so they are typically used for high-end applications. These coatings are available in multiple colors and can be applied using flexo, screen, or roll coater.

Metallic or Foil Effect
Metallic inks have been in use for several years, but they do not come close to providing the highly reflective appearance and brilliance offered by metalized papers, foil laminations, and cold or hot foil stamping. However, recent innovations in coatings technology have resulted in break-through improvements in the brilliance that can be achieved with UV-curable metallic coatings. The higher application amounts typically applied with metallic coatings (v. metallic inks) can achieve effects that are equally brilliant to foil laminations. In addition, these coatings can be applied to precise areas, reducing waste and saving time and energy through process efficiencies. Moreover, these metallic coatings are easily removed in the repulping process.

Holographic
One of the most interesting and visually attractive effects currently in use involves the use of holographic laminated films or stamps. This same holographic effect can actually be achieved using a UV-curable coating. This involves the use of a reusable micro-embossed film that transfers the holographic image to the uncured UV coating, commonly known as Cast & Cure™ (a trademark of Breit Technologies, Lenexa, Kan.). The UV coating is then cured through the film to create the holographic pattern. This process either can be done in-line or off-line, but requires expensive unwind and rewind equipment to handle the micro-embossed film. It does, however, eliminate the need to send paperboard out for laminating with a holographic film and then overprinting the board. Also, the resulting holographic effect is a coating instead of a piece of plastic film, resulting in improved recyclability. Holographic coatings can be spot-applied.

Soft Touch
Soft touch coatings are unique water-based finishes that deliver the feel and appearance of a velvet or flocked fabric substrate. These are typically two- part coatings that have been used for several years in the automotive industry. Although currently in development by multiple suppliers, a UV-curable version that has the same look and feel of the water-base soft touch coatings has not yet been perfected.

In today’s sound-byte society, the amount of time available to capture a reader’s attention is becoming shorter and shorter. The use of specialty UV coatings for off-line print finishing is nothing new. However, there are some interesting new coatings and techniques currently in use that not only create stunning sensory effects but also lend themselves well to use by most print finishers.

Kris Getty is market segment director at Henkel Corporation (formerly Sovereign/Pierce & Stevens), a leading supplier of specialty UV and other coatings for print finishing and packaging applications. Henkel supplies all of the coatings discussed in this article. Many of the effects created by the above coatings are highly visual and need to be seen coated on paper. For more information, call (866) 4HENKEL (866-443-6535) or visit www.henkelna.com/miracure.